'05 YZ 450f, New Top End?

Hello All,

How do you know when you need a Top End...I check my valves a few times a year, change my oil way too much, clean my air filter all the time but i just want to know what to look for.

I just cant afford a little problem turning into something too expensive...


When your valves need to be shimmed two sizes (.10mm) smaller, and/or won't stay adjusted more than a few hours, you need valves.

When the engine fails a leak down test, you need rings, and possibly a piston. More than a 10-15% loss in a leak down is usually pretty much a failed test, but that depends a great deal on the particular tester used, as there is no real standard by which they are made.

You can also go by time or mileage, and a visual inspection of the piston and bore. The life of the bore itself can sometimes be almost doubled by replacing a piston before it quite really needs it.

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